1. Field of the Invention
The present invention relates to a method of threading in a false twisting machine in which a yarn is oiled after processing a yarn false twists and taken up on a package.
2. Prior Art
First, the general construction of a false twisting machine will be described with reference to FIG. 6. Each of yarns Y pulled out from yarn packages 51 supported on a creel 50 is stretched between a first feed roller 53 and a second feed roller 54 at a yarn tension for drawing. A false twisting device 55, such as a belt-type false twisting device, is disposed between the feed rollers 53 and 54 near the second feed roller 54. The false twisting device 55 inserts twists in a portion of the yarn Y extending on the feed side of the false twisting device 55 and untwists a portion of the yarn Y extending on the delivery side of the false twisting device 55. A primary heater 56 for heat-setting the yarn Y is disposed between the feed rollers 53 and 54 near the first feed roller 53 to heat the twisted portion of the yarn Y to a drawing temperature. A third feed roller 57 is disposed after the second feed roller 54, and a secondary heater 58 is disposed between the feed rollers 54 and 57 to reheat the yarn Y when necessary. The reheated yarns Y are wound in textured yarn packages 60 by a take-up winder 59.
Each of oiling rollers 1 is disposed between the third feed roller 57 and the take-up winder 59. The yarn is oiled with the oiling roller 1 before taking up to ensure that the yarn can be smoothly unwound from the package. When a textured yarn package becomes a full package, a traveling doffer 66 transfers the full package 60 from the take-up winder 59 to a rotary creel 63 and puts an empty bobbin on the take-up winder 59. The traveling doffer 66 travels along a rail 68 extended on a passage between a false twisting machine body 61 and the primary heater 56. The traveling doffer 66 travels along the false twisting-machine body 61 to doff full packages and to put empty bobbins on the take-up winder 59.
The traveling doffer 66 will be described hereinafter with reference to FIG. 5, in which FIG. 5a is a front view and FIG. 5b is a side view of the traveling doffer 66. The traveling doffer 66 has three doffing units each consisting of a chucking hand 75, a package support 76, a bobbin chuck 77 and a cradle opener 78. The cradle opener 78 opens the cradle of the false twisting machine body 61 supporting a full package 60, the chucking hand 75 holds the full package 60, the package support 76 supports the full package 60, the bobbin chuck 77 takes an empty bobbin from the rotary peg 63 and puts the empty bobbin on the cradle, and then, the package support 76 puts the full package 60 on the rotary peg 63 shown in FIG. 6. A threading device 70 is mounted for vertical movement on the travelling doffer 66. A nozzle included in a positioning device 72 blows air and a suction nozzle 71 sucks the free end of the yarn and attaches the free end of the yarn to the empty bobbin. Since the false twisting machine body 61 operates continuously while the yarn is cut to doff the full yarn package and the threading device 70 attaches the free end of the yarn to the empty bobbin, the suction nozzle 71 continues to suck the free end of the yarn to prevent the yarn from slacking.
As shown in FIG. 4, the positioning device 72 has a screw jack 41 connected to a driving device 40 to move two wheels 42 and 43 laterally, as viewed in FIG. 4. The Screw jack 41 fits the two wheels 42 and 43 in grooves 44 and 45 formed in the false twisting machine body 61 for positioning. The positioning device 72 is provided with a nozzle 73. The nozzle 73 is advanced together with the two wheels 42 and 43 as far as the nozzle 73 is joined to a coupling 74. Then, compressed air is supplied in the direction of the arrows 1 and 2 through a pipe to the suction nozzle 71 of the threading device 70 to use the compressed air for sucking the free end of the yarn (FIG. 6).
The operation of the threading device 70 will be described hereinafter with reference to FIG. 3, in which FIG. 3a shows the threading device 70 in a free end sucking operation and FIG. 3b shows the threading device 70 in a threading operation. When the textured yarn is wound in a full package 60, a cutter, not shown, cuts the yarn at a position on the delivery side of the oiling roller 1 and, at the same time, the suction nozzle 71 starts sucking the free end of the yarn. During this operation, the threading device 70 is positioned at a lower position a with respect to the traveling doffer 66 as shown in FIG. 3a. After the full package 60 has been transferred to the rotary peg 63 and an empty bobbin 67 has been transferred from the rotary peg 63 to the cradle of the false twisting machine body 61, the threading device 70 is raised to positions b, c and d sequentially to attach the free end of the false twisted yarn to the empty bobbin 67.
Since this method of threading in a false twisting machine cuts a portion of the yarn extending on the delivery side of the oiling roller and sucks the free end of the yarn, the free end of the yarn must be pulled by a suction force exceeding the viscous resistance of the oil. Recently, the operating speed of the false twisting machine has been progressively increased to increase the yarn speed from about 800 m/min to 1000 m/min or above. Since the viscous resistance of the oil is proportional to the square of the yarn speed, the oiling roller resists greatly against the running of the yarn particulary in a cold season, such as winter, in which the viscous resistance of the oil increases, so that the suction nozzle is liable to fail in sucking the free end of the yarn due to the slacking of the yarn.